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    Copyright (c) 2001-2011 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at
#if !defined(FUSION_TAG_OF_09232005_0845)
#define FUSION_TAG_OF_09232005_0845

#include <boost/fusion/support/config.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/remove_const.hpp>
#include <boost/fusion/support/tag_of_fwd.hpp>
#include <boost/fusion/support/detail/is_mpl_sequence.hpp>
#include <boost/mpl/has_xxx.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/assert.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/mpl/if.hpp>
#include <boost/config/no_tr1/utility.hpp>

namespace boost
    template <typename T, std::size_t N>
    class array; // forward

    namespace tuples
        struct null_type;

        template <
            class T0, class T1, class T2, class T3, class T4,
            class T5, class T6, class T7, class T8, class T9
        class tuple;

        template <class Head, class Tail>
        struct cons;

namespace boost { namespace fusion
    struct non_fusion_tag;
    struct mpl_sequence_tag;

    namespace detail

        template <typename Sequence, typename Active>
        struct tag_of_impl
          : mpl::if_<fusion::detail::is_mpl_sequence<Sequence>,
              mpl::identity<non_fusion_tag> >::type

        template <typename Sequence>
        struct tag_of_impl<
          , typename boost::enable_if<detail::has_fusion_tag<Sequence> >::type>
            typedef typename Sequence::fusion_tag type;

    namespace traits
        template <typename Sequence, typename Active>
        struct tag_of
            : boost::fusion::detail::tag_of_impl<Sequence, Active>

    namespace detail
        template<typename T>
        struct tag_of
            : traits::tag_of<typename remove_const<T>::type>